This application makes reference to, incorporates the same herein and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application entitled MICROWAVE OVEN earlier filed in the Korean Industrial Property Office on the 19th day of August 2000, and there duly assigned Ser. No. 48178/2000.
1. Field of the Invention
This invention relates in general to microwave ovens, and more particularly, to a microwave oven having a safety device of the door thereon, with a simplified circuit structure.
2. Description of the Related Art
Conventionally, a microwave oven includes a main casing having a cooking chamber and an electronic component chamber, a door for opening and closing an opened front part of the cooking chamber, and a control panel provided in the main casing, for driving a number of components in the microwave oven. In the component chamber are provided a high-voltage transformer generating high-voltage based on an electric power supplied from a power supply part, and a magnetron generating electromagnetic waves based on the high-voltage generated by the high-voltage transformer.
The microwave oven is equipped with a safety device to prevent the electromagnetic waves from being supplied into the cooking chamber while the door is being opened. The safety device includes a latch member mounted in the door so as to be engaged with a pair of hook holes provided in the front part of the cooking chamber, and a group of switches, so called a safety switch part, which are connected on or off depending upon the opening and closing of the door. The latch member includes a pair of hooks fitted into the hook holes; and the safety switch part includes a first door switch, a second door switch and a monitor switch capable of controlling the on-and-off operation thereof depending upon the operation of the hooks of the latch member.
Hereinafter, the conventional safety device for the door will be described in more detail with reference to a detailed circuit diagram shown in FIG. 5.
The conventional microwave oven has a power supply part 130, a high-voltage transformer 131 generating high-voltages based on the electric power supplied from the power supply part 130, and a magnetron 133 generating electromagnetic waves generated based on the high-voltages from the high-voltage transformer 131. In the microwave oven is provided a safety switch part cooperating with opening and closing of the door (not shown) on the microwave oven. The safety switch part includes a first door switch 145 operated so as to be switched on by pressure by the hook (not shown) of a latch member (not shown), and a second door switch 147 operated to be switched on and off according to a control signal inputted through a control panel (not shown).
Referring to the illustrated circuit diagram, a first current line L2 and a second current line L3 are provided to both ends of a primary coil of the high-voltage transformer 131. A common current line L1 is installed between the first and second current lines L2 and L3, forming a closed loop by being combined with one another.
On the common current line L1 are provided power supply part 130, and a fuse 135 for cutting off overcurrent. Between the common current line L1 and the first current line L2 are provided a lamp 137 connected in parallel to the common current line L1, for illuminating the inside of the cooking chamber, and a relay switch 141 connected in series to the lamp 137, for controlling the on-and-off operation of the lamp 137. Between the common current line L1 and the first current line L2 are also provided a fan motor 139 connected in parallel to the common current line L1, for activating a fan (not shown), and a relay switch 143 connected in series to the fan motor 139, for controlling the operation of the fan motor 139. A pair of monitor switches 149 are respectively provided between the common current line L1 and the first current line L2, and the common current line L1 and the second current line L3. The monitor switches are closed when the door is being opened whereas they are opened when the door is closed.
With this configuration, the first door switch 145 and the second door switch 147 are switched-off when the door is opened, thereby cutting off the electric power supplied into the magnetron 133. Consequently, the electromagnetic waves from the magnetron 133 cannot be applied into the cooking chamber while the door is being opened.
In the conventional microwave wave oven equipped with a safety device detecting opening and closing of the door, in order to provide more effective safety devices, it would be necessary to reduce the number of the safety switches and have a simplified configuration of the circuit, thereby saving the cost of production and avoiding the complexity of the circuits"" configuration.
Therefore, the present invention has been made in view of the above need, and it is an object of the present invention to provide a microwave oven with a safety device having a simplified configuration of circuits by decreasing the number of switches.
This and other objects of the present invention may be achieved by a provision of the microwave oven including a main casing with a cooking chamber, a door for opening and closing the cooking chamber, and a magnetron in the main casing, for heating food within the cooking chamber, the microwave oven further includes a power supply part; at least a first door switch closed while the door is closed so as to supply electric power from the power supply part into the magnetron; a monitor switch connected in series to the first door switch, being operated in reverse relative to the opening and closing of the first door switch; and a control part determining that the first door switch is in trouble where the first door switch and the monitor switch are not operated in reverse to each other, and preventing the electric power from being supplied into the magnetron when the door is opened under the state that the first door switch is closed.
Preferably, the microwave oven further includes a fuse being provided between the power supply part and the first door switch, for cutting off overcurrent, and where the control part short-circuits the fuse when the door is opened while the first door switch and the monitor switch are both closed.
The control unit preferably supplies an electric power to a driver a switching element when the first door switch is closed.
More preferably, the microwave oven further includes a second door switch operated in conformity with the opening and closing of the first door switch, and cooperating with the first door switch, allowing the electric power from the power supply part so as to be supplied into the magnetron when the door is closed.